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<a name="boost_typetraits.user_defined"></a><a class="link" href="user_defined.html" title="User Defined Specializations">User Defined Specializations</a>
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<p>
      Occationally the end user may need to provide their own specialization for
      one of the type traits - typically where intrinsic compiler support is required
      to implement a specific trait fully. These specializations should derive from
      boost::<a class="link" href="reference/integral_constant.html" title="integral_constant">true_type</a>
      or boost::<a class="link" href="reference/integral_constant.html" title="integral_constant">false_type</a>
      as appropriate:
    </p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">is_pod</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">is_class</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">is_union</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">struct</span> <span class="identifier">my_pod</span><span class="special">{};</span>
<span class="keyword">struct</span> <span class="identifier">my_union</span>
<span class="special">{</span>
   <span class="keyword">char</span> <span class="identifier">c</span><span class="special">;</span>
   <span class="keyword">int</span> <span class="identifier">i</span><span class="special">;</span>
<span class="special">};</span>

<span class="keyword">namespace</span> <span class="identifier">boost</span>
<span class="special">{</span>
   <span class="keyword">template</span><span class="special">&lt;&gt;</span>
   <span class="keyword">struct</span> <a class="link" href="reference/is_pod.html" title="is_pod">is_pod</a><span class="special">&lt;</span><span class="identifier">my_pod</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">{};</span>

   <span class="keyword">template</span><span class="special">&lt;&gt;</span>
   <span class="keyword">struct</span> <a class="link" href="reference/is_pod.html" title="is_pod">is_pod</a><span class="special">&lt;</span><span class="identifier">my_union</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">{};</span>

   <span class="keyword">template</span><span class="special">&lt;&gt;</span>
   <span class="keyword">struct</span> <a class="link" href="reference/is_union.html" title="is_union">is_union</a><span class="special">&lt;</span><span class="identifier">my_union</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="reference/integral_constant.html" title="integral_constant">true_type</a><span class="special">{};</span>

   <span class="keyword">template</span><span class="special">&lt;&gt;</span>
   <span class="keyword">struct</span> <a class="link" href="reference/is_class.html" title="is_class">is_class</a><span class="special">&lt;</span><span class="identifier">my_union</span><span class="special">&gt;</span> <span class="special">:</span> <span class="keyword">public</span> <a class="link" href="reference/integral_constant.html" title="integral_constant">false_type</a><span class="special">{};</span>
<span class="special">}</span>
</pre>
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